Characterization of endothelin(A) receptors in cerebral and peripheral arteries of rat

We have characterized and quantified endothelin receptors in rat brain (anterior cerebral) and peripheral (aorta, carotid, and caudal) arteries, with the use of [I-125]endothelin and quantitative autoradiography. Endothelin binding was saturable, of high affinity, and totally displaced by the selective endothelin ET(A) antagonist BQ 123. A single class of ET(A) receptors is located in the medial layer of peripheral and cerebral arteries, and its quantification by autoradiography allows study of their regulation and function

Characterization of endothelin(A) receptors in cerebral and peripheral arteries of rat

We have characterized and quantified endothelin receptors in rat brain (anterior cerebral) and peripheral (aorta, carotid, and caudal) arteries, with the use of [I-125]endothelin and quantitative autoradiography. Endothelin binding was saturable, of high affinity, and totally displaced by the selective endothelin ET(A) antagonist BQ 123. A single class of ET(A) receptors is located in the medial layer of peripheral and cerebral arteries, and its quantification by autoradiography allows study of their regulation and function

Structural and functional characterization of an acidic platelet aggregation inhibitor and hypotensive phospholipase A(2) from Bothrops jararacussu snake venom

An acidic (pI similar to 4.5) phospholipase A(2) (BthA-I-PLA(2)) was isolated from Bothrops jararacussu snake venom by ion-exchange chromatography on a CM-Sepharose column followed by reverse phase chromatography on an RP-HPLC C-18 column. It is an similar to13.7 kDa single chain Asp49 PLA(2) with approximately 122 amino acid residues, 7 disulfide bridges, and the following N-terminal sequence: 'SLWQFGKMINYVMJGESGVLQYLSYGCYCGLGGQGQPTDATDRCCFVHDCC(51). Crystals of this acidic protein diffracted beyond 2.0 Angstrom resolution. These crystals are monoclinic and have unit cell dimensions of a = 33.9, b = 63.8, c = 49.1 Angstrom, and beta = 104.0degrees. Although not myotoxic, cytotoxic, or lethal, the protein was catalytically 3-4 tithes more active than BthTX-II, a basic D49 myotoxic PLA(2) from the same venom and other Bothrops venoms. Although it showed no toxic activity, it was able to induce time-independent edema, this activity being inhibited by EDTA. In addition, BthA-I-PLA(2) caused a hypotensive response in the rat and inhibited platelet aggregation, Catalytic, antiplatelet and other activities were abolished by chemical modification with 4-bromophenacyl bromide, which is known to covalently bind to His48 of the catalytic site. Antibodies raised against crude B. jararacussu venom recognized this acidic PLA(2), while anti-Asp49-BthTX-II recognized it weakly and anti-Lys49-BthTX-I showed the least cross-reaction. These data confirm that myotoxicity does not necessarily correlate with catalytic activity in native PLA(2) homologues and that either of these two activities may exist alone. BthA-I-PLA(2), in addition to representing a relevant molecular model of catalytic activity, is also a promising hypotensive agent and platelet aggregation inhibitor for further studies. (C) 2002 Elsevier B.V. All rights reserved